IL4 and ischemic disease: here we examine the effect of pro-inflammatory (LPS) and anti-inflammatory (IL-4) macrophage on ischemic diseases in a mouse ischemic hindlimb and heart model, and identify that signal regulatory protein α (Sirpα) modulates macrophage polarization induced angiogenesis via promoting phagocytosis or activating HIF1α nucleus relocation in macrophages, respectively.